Women engaged in sports or the like activities typically use special brassieres (or bras) to support their breasts and thus avoid excessive movement and/or bounce due to the activities or motions associated with such sports. Modern sports bras typically employ one of two designs to provide extra support: encapsulation or compression. Encapsulation designs (typically molded designs) provide a more natural shape and better definition of the breasts, while compression designs are better at minimizing bounce of the breasts. Many encapsulation designs also use under-wires to offer extra shaping and support to the bust, with a loss of comfort that results from adding an inflexible support to a bra designed for use when the user's body including the breasts are in motion.
Most sports bras are designed with either a racer back designed to offer back support and keep straps in place, or a conventional back that offers the best adjustment of the individual back straps and ease of wearing but which has reduced back support.
All sports bras are designed with specific degrees of support or compression, based upon the nature of the intended activities or motion. High impact activities such as running require high compression to minimize bounce, while low impact activities such as yoga require only low compression to minimize bounce. Further, each woman has her own preference as to how much compression and resulting bounce is appropriate, desirable and/or comfortable. Bras designed for compression typically only offer a fixed amount of compression for a given garment. Bras of this type are characterized as high, medium, or low compression garments based on their design.